A series of studies to evaluate the clinical validity of the Acuity Card (AC) Procedure is proposed,. This new, rapid method to test visual acuity of infants and young children combines subjective, clinical judgments with the preferential looking (PL) technique. Of all PL procedures, it is the most efficient for routine clinical use. Visual acuity of each eye in a patient can be assessed in 2 to 5 minutes, only one examiner is required, and test materials are simple. Although the AC procedure has been readily incorporated into clinical practice in some settings adequate normative data with which to interpret acuities in pediatric ocular disorders are lacking. In addition, the criterion-related validity of the AC procedure has not been evaluated. And, the potential for bias in the AC procedure, that is, the possibility that the examiner's expectations rather than the infant's behavior determines the infant's acuity, has not been adequately studied. In Part I, normative data on the monocular acuity of 600 infants and young children between 1 month and 4 years with normal eyes will b obtained. In Part II, three studies of 750 pediatric patients with diverse ocular disorders will be conducted. Study IIA will evaluate the influence of bias or examiner expectation on the Acuity Card acuities. Study IIB will compare AC acuity to clinical recognition acuity in 3- and 4-year-old children with various ocular conditions. And Study ICC will compare AC acuity to PL acuity obtained with a lengthier, more objective technique in patients between age 1 month and 24 months. This research will be conducted by six clinical research centers, all experienced in testing PL visual acuity of young subjects and committed to the goals of this project. The heterogeneous normal and diverse patient populations available in these centers will ensure generalizability of the results to other clinical settings. This project will help establish a standard, behavioral test for routine clinical assessment of visual acuity of pediatric patients.